Synthetic antioxidant preservatives are added to a wide variety of products during processing and storage. The types of products include foods, plastics and packaging materials. When an oxidizing event takes place in a product, the antioxidant molecules rapidly react to form antioxidant radicals. This reaction protects the product from damage resulting from the oxidizing event and consequently increases the shelf life of the product. Common synthetic antioxidant preservatives include butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tert-butylhydroquinone (TBHQ), di-tert-butylhydroquinone (DTBHQ), and propyl gallate. There are also naturally occurring antioxidants, which include sesamol, sesamin, vitamin A and beta-carotene, vitamin E and tocopherols and vitamin C.
The use of antioxidant preservatives is particularly common in foods with significant unsaturated lipid content. These foods also contain quantities of unsaturated fatty acids. Unsaturation in fatty acids makes lipids susceptible to oxidation, which in turn leads to complex chemical changes in the lipids. These chemical changes eventually manifest themselves in the development of off-flavors (rancidity) in foods. The oxidation of unsaturated fatty acids is typically mediated by free radicals, which can be caused by heat, light, ionizing radiation, trace metals and some proteins. The use of antioxidant preservatives in lipid-containing foods minimizes rancidity, retards the formation of toxic oxidation products, allows maintenance of nutritional quality and increases the shelf life. The mechanism by which the antioxidant preservatives are believed to act involves scavenging peroxyl radicals and preventing propagation of the oxidation process. The antioxidant activity of these compounds is lost upon scavenging a free radical, so a food or other product is no longer protected from oxidation once all the antioxidant preservative has reacted with a free radical. In other words, the degree of protection from oxidation depends on the quantity of antioxidant preservative that is present.
Unfortunately, there are restrictions on the amount of synthetic antioxidant preservatives that can be added to a product, especially products intended for human or animal consumption. The U.S. Food and Drug Administration limits the amount of BHA and BHT in foods to 0.02% of total fat, because these compounds are suspected to be carcinogenic.
Consequently, there is a need for a new class of synthetic antioxidant preservatives that are less toxic to humans and animals. Also, it would be advantageous to develop an antioxidant preservative with increased potency and the ability to be readily processed with a variety of materials. Antioxidant preservatives with these improved properties would increase the shelf life and palatability of lipid-containing food items, as well as other products containing moieties (e.g., unsaturated carbon-carbon bonds) that can be damaged by free radicals.